View full sizeTyler Tjomsland / The OregonianA memorial for shooting victim Shalamar Edmond consisting of stuffed animals and a shot of alcohol sit near a North Columbia playground on Wednesday, May 18, 2011. Police say their efforts to solve murders like Edmond's are frustrated by a "code of silence."

Portland police investigators are frustrated by a "code of silence" among gang members that has kept officers from solving two gang-related homicides from last year and one this year where a host of witnesses likely saw something, Assistant Chief Eric Hendricks says.

He cited the killings of Shalamar Edmond, 18, in New Columbia's McCoy Park last May 16; Leonard Irving Jr., 34, across the street from a nightclub on Northeast 82nd Avenue last June 26; and the fatal shooting of bouncer Robert Greene, 30, on Feb. 19 outside the Grand Central Restaurant and Bowling Lounge.

"All three of these are examples of cases where there's folks in the community who could help us get these killers off the street," Hendricks said Friday at a meeting of the city's Gang Violence Task Force, made up of police, city and county leaders, outreach workers and community members.

"My plea is to the community: If you know – even if you think you may know what happened -- please call homicide detectives," Hendricks said.

So far this year, Portland's Gang Violence Response Team has fielded 37 call-outs for shootings, fights or stabbings compared with 26 by the end of April last year. The team was called out 103 times to gang-related violence in 2011, the most in 10 years.

"We are on pace to exceed that easily," Chief Mike Reese told city commissioners last week. "They're shooting up our community."

Irving's mother, Lucy Mashia, was among community members who attended the gang task force meeting. Directing his remarks to her, Hendricks said detectives believe Irving was the "unintended victim" of a gang shooting. Irving had been celebrating his nephew's 21st birthday the night he was killed, shot four times in the back. His nephew was wounded.

"We believe there are folks out there who saw who shot Mr. Irving," Hendricks said. "Without the community coming together and providing the information we need, these won't be solved."

Hendricks added: "Mrs. Macia, we're not going to forget the death of your son."

Deputy District Attorney Pat Callahan, who prosecutes offenders tied to gang violence in Multnomah County, said the so-called "G-code" or code of silence extends beyond gang members.

"There's a glorification of the thug lifestyle, which includes 'don't be a snitch,' " Callahan said. "It's far-reaching beyond gangs. It's a huge problem. I have no idea how to address it. I always think it starts at home."

City leaders are working with relatives of victims of gang violence to draw attention to the problem, and encourage them to speak out against the "silence" of witnesses.